Teletypewriter transmitting and receiving system



Nov. 11,1941. w. Y. LANG v 2,262,014

TELETYPEWRITBR TRANSMITTING AND RECEIVING SYSTEM Filed May 3, 1940 PERFORA ran INVENTOR W. 1. LANG Patented Nov. 11, 1941 TELETYPEWRITER TRANSMITTING AND RECEIVING SYSTEM Wilmarth Y. Lang, Towaco, N. J., assignor to Bell Telephone Laboratories, Incorporated, New

York, N. Y., a corporation of New York Application May 3, 1940, Serial No. 333,062

19 Claims.

This invention relates to teletypewriter systems and more particularly to an improvement in such systems to compensate for differences in the speed of operation of different receiving teletypewriter motors in situations wherein more than one teletypewriter receiver is connected to a single transmitter from which the receivers are receiving signals simultaneously. As is well known one of the difiiculties encountered in such operation is caused by the variations in speed between the different machines caused by differences in speed of their driving motors and by variations in clutch grip time and clutch slippage.

An object of this invention is the improvement in the operation of teletype'writer systems wherein a single transmitting device transmits simultaneously to a group of teletypewriter receiving devices.

A more particular object of this invention is the improvement of a teletypewriter system wherein a single transmitter operates with a group of receivers so that the machines may be maintained in proper synchronism.

A feature of the invention herein is a means for compensating for variations in the speeds of teletypewriter machines.

A further feature of the invention is means for stopping the transmission of signals from a teletypewriter transmitter, in cases Where the lengths of time required for the performance of a par ticular function is difierent for the different receiving machines until all of the receiving ma-' a home teletypewriter receiver and three remote receivers. The starting and stopping of the distributor is governed by a special control circuit including a delay circuit responsive to a contact under control of a function lever in the home teletypewriter receiver.

The invention herein is shown incorporated into the teletypewriter system disclosed in Patent 2,055,567 to E. F. Watson, September 29, 1936 and the disclosure of Patent 2,055,567 is hereby made a partof the disclosure of the invention herein,

in so far as it is necessary to an understanding thereof. 7

In Patent 2,055,567 as in the patent. herein, a perforator is shown at .the right of the drawing. In the perforator a tape is perforated in accordance with a, code. The tape is fed over a number of pins to actuate a system of levers which in turn controls a group of tongues. The tongues open or close five circuit paths connecting one side of a telegraph loop with another through segments of a transmitting distributor. As the transmitting distributor shaft is rotated, by its motor through a clutch, worm and gear, a brush arm is rotated and metallic portions wiped over the distributor rings to connect successive segments on one ring to the solid. ring. If a hole has been punched to admit a pin into the tape, the corresponding tongue is actuated so that the circuit path is closed across the loop, over a path from one side of the loop through the tongue, its corresponding contact and segment and the solid ring to the opposite side of the loop. If a hole is not punched in the tape opposite a particular pin, the pin is not admitted.- The corresponding tongue is not actuated. "The tongue remains in engagement with its lower or spacing contact. The loop remains open as the brush rotates across the corresponding segment and a spacing signal is transmitted. I

The transmitter-distributor shaft is driven by a motor coupled through a clutch to a worm -in turn releases the stop arm to engage the pe-.

ripheral shoulder on the stop cam to stop the rotation of the transmitter-distributor arm.

The tape is advanced from the perforator to the tape pins by means of the feed wheel which engages a continuous row of holes lengthwise of the tape. The feed wheel is rotated through a ratchet wheel by a feed pawl mounted on one arm of a feed lever, shown to the left of the five contact levers. The feed levers are operated by a bail, under the influence of an operating lever controlled in turn by the tape feed operating cam mounted on the bottom of the vertical main shaft of the transmitting distributor.

All of this is described in complete detail in Patent 2,055,567 to which reference has been made above.

In Patent 2,055,567 the tape controlled transmitting distributor is disclosed in a system in which it transmits from a home station, over a telegraph loop circuit connecting the home station with a central office through the central office, over a connecting telegraph loop circuit to a single teletypewriter receiver located at a connected local station. In the arrangement of the invention herein there are a plurality of teletypewriter receivers located at separate local stations connected by means of a telegraph loop circuit through the central office to the single transmitter. For convenience these receiving stations, indicated R. S. I, R. S. 2 and R. S. 3, are shown connected by means of a single loop circuit extending through the three receiving stations in series. It is to be understood that the receiving stations will ordinarily be connected to the central ofiice in parallel, by means of separate loops. The series arrangement, however, will illustrate the invention equally well and requires less space on the drawing.

In addition to the three receiving stations connected at the distant end of the line, there is also connected to the tape controlled transmitting distributor a home teletypewriter transmitter and receiver designated H, Tty, T, and R. This is locatedin the same oflice'with the tape controlled transmitter and adjacent the transmitter.

In the operation of the system of the invention herein, the tape controlled transmitter-distributor transmits through the central office to i the three distant teletypewriter receiving sta- 'withthe loop connecting the transmitter-distributor through the central station to the distant receiving stations.

The loop circuit may be traced from the rightbridging the gap between the segment and the solid ring to which the top loop conductor is connected. The loop is completed over the top conductor, through the selector magnet 2 and the teletypewriter transmitting contacts and break key of the home station to the left-hand side of the central battery.

A total of five shunt paths, corresponding to that traced through contact 8, interconnect the top and bottom loop conductors. These may be open or closed depending on whether or not a corresponding hole has been punched in tape I to control the tongue contact such as 8. As each shunt takes its position in turn across the loop conductors, when the transmitter-distributor arm sweeps across the corresponding segment, the loop will be open or closed to transmit a marking or a spacing signal element. The loop is always closed when the arm is on the stop segment, as the bottom loop conductoris connected to that segment directly, and the gap between the stop segment and the solid inner ring of the distributor, to which the top loop conductor is directly connected, is bridged by the arm brushes when the brush is on the stop segment. The start signal element is always an open or spacing signal element, because the bottom conductor is hand side of the battery at the central oflice C. O.

over the top conductor, through the receiving teletypewriter at receiving stations I, 2 and 9 in series, through the central office to the transmitting oiilce by means of the bottom loop conductor, through conductor 3 and conducting shaft 4 to the tongues, such as 5, arranged in parallel. If, in accordance with the code, no hole has been punched in the tape 1 to admit the pin 8, the tongue 5 will be in position shown and the particular shunt across the loop, corresponding to the tongue 5, will be open at the contact 8. A

A spacing signal will be transmitted when" arm 9 sweeps across the segment corresponding to ceiving stations.

not connected in any manner to the start segment and as the brush arm sweeps across the start segment the loop circuit will be open.

In addition to transmitting trains of signal elements each comprising a start impulse, five signal impulses to cause the selection of a particular character by the receiving printer and a stop impulse, the modern teletypewriter transmitter and receiver must transmit and receive trains of signals to perform various functions, such as to shift from letters to numerals, etc., operate the line feed to step the receiver printer up to the next line, to return the carriage from right to left, to step thereceiving printer through a succession of lines and spaces as in tabulating as well as to stop the receiver motor automatically and other functions. The manner in which this is performed by the receiver is well known and is described in detail in Patent 1,904,164 to S. Morton, April 18, 1933. In the performance of certain of these functions, when a single transmitter is transmitting to a plurality of receivers, it is important that the transmission of characters should not be resumed until all of the machines have completed the function which the transmitted signal conditions each receiver to perform. As is'well understood by those skilled in the art and as is described in Patent 1,904,164 mentioned above, which is hereby made a part of this disclosure in so far as it may be necessary to an understanding of the present invention, the impulses transmitted by the transmitting distributor are impressed on a selector magnet such as 2 in the receiving printer at each of the re- This magnet corresponds to magnet 9 shown in Fig. 4 of Patent 1,904,164. The selector magnet makes a selection, either of a particular type bar which is actuated under control of the teletypewriter receiving motor to print type, or of a function lever, which is actuated under control of the receiving motor to perform a function such as suggested above.

In the performance of a number of functions, such, for instance, as in tabulating, after the selection of the particular function lever which is to perform the function, the function is completed under the control of the individual teletypewriter receiving motor at each station. In

the'pe'rformance of these functions the individual teletypewriter receivers require a relatively long operating period. The motors, since each is under local control subject to variations in voltage, etc., of thelocal supply circuit, require intervals of different lengths to complete the designated'function. Variations in clutch grip time and clutch slippage also tend to displace the receivers from uniform alignment. If thetransmission of signals is resumed'before all of the receivers have completed the designated function, all of the machines will not be in proper condition to record the resumed signals.

Applicants invention is designed to obviate the difficulties ensuing from the lack of uniformity in speed of all of the receiving printers. Applicant solves this problem by identifying the transmission of each signal train from the tape controlled transmitting distributor which involves the performance of a function by a group of receivers to which the transmitter is connected, the performance of which function requires so much time that the variations in speed of the teletypewriter receiving motors will cause difficulty. The particular signal train in passing through the selector magnet of the home teletypewriter receiver operates a function lever in the home receiver. This function lever controls a contact which in turn controls the transmitter-distributor stop magnet through a relay and a delay circuit. When the particular function signal train is transmitted and registered in the home teletypewriter receiver, the transmitting distributor is stopped by the opening of the contacts such as H, which releases a relay such as I2, which in turn releases stop magnet l3, which permits stop lever I4 to be actuated by spring I5 so as to engage the peripheral shoulder I6 of stop cam I! and stop the rotation of the vertical shaft of the transmitting distributor I. After the function has been completed by the home teletypewriter receiver the contact H is again closed. The relay I2 is not immediately reoperated as the relay circuit is then under control of a delay circuit comprisingthe tube, I8

and condenser I9 which measures an interval before the relay is permitted to reoperate. The delay interval interposed between the reclosing of contact |I, after the completion of the function by the home teletypewriter receiver and the releasing of the transmitter-distributor shaft so that the transmission of signals may be resumed, is fixed at a period at least equal to, if not slightly greater than, the difference between the time required by the home receiver to complete its function and the time required bythe slowest of the receiving printers at the station such as R. S. I, R. S. 2 or R. S. 3 to complete the same 'function.' By this means when the transmitter-distributor I resumes transmission all of the receivers will have completed the function and all will be in condition to resume receiving. The delay introduced by..the delay circuit may be fixed at the interval necessary to compensate for the greatest interval required for the particular function based on the speed variations to which the various local receiving mo-Q tors are subject.

The operation of the transmitting distributor start-stop control including the delay feature magnet I3.

then be traced from the positive terminal of battery 20 through-contact II, conductor 2|, contact 22 of relay I2, the right-hand winding of relay I2 and conductor 23 to the negative terminal of battery 20. This operates relay 22 which is thus normally maintained in the operated position as shown.

When the manually operated switch 25 is closed, a circuit may be traced from ground 24, through switch 25. When there is sufficient slack in the tape, the automatic stop lever 23 is lowered, closing contacts 21, and the circuit is extended over conductor 28, through closed contacts 29 of relay I2 and the winding of magnet |3 to battery. Magnet I3 is operated rotating stop lever I4 to disengage from the peripheral shoulder of stop cam I1, permitting the vertical shaft of the transmitter-distributor to rotate. Magnet I3 remains energized normally and the transmitter-distributor continues to transmit.

When a code symbol for a particular function is punched by the perforator, the performance of which function requires a relatively long period of I time and the performance of'which function requires different intervals for the different receivers, in accordance with this invention, delay is interposed between the completion of the function by the home receiver and the resumption of transmission by the transmitterdistributor, to compensate for the variations so that transmissionis not resumed until the function has been completed by the slowest receiver. This is performed as described now in detail.

When the home teletypewriter selector magn't receives the signal train for the function from the transmitter-distributor, and simultaneously with the start of operation of the mechanism in the home teletypewriter receiver to perform the function, contact II is opened. When it opens the operating path for relay l2, traced in detail above, is opened, deenergi'zing relay I2 which releases. Contact 29 is thereupon opened. This breaks the .energizing path of stop Stop arm I4 is thereupon released and rotated by spring "Hi about its pivot so that its right-hand end is interposed in the path of peripheral shoulder I6 of stop cam H which stops the rotation of the transmitter-distributor.

The mechanism of the home teletypewriter receiver continues to operate in a well-known manner under the influence of its own local motor (not shown). Upon the completion of the function contact II is again closed. In tracing the path over which relay-l2 was normally energized, the circuit was traced through contact 22. When the relay released, this path was broken. When contact recloses, as described above, relay I2 cannot operate over its normal energizing path. The circuit now may be traced from the positive side of battery 20, through contact conductor 2|, contacts 30, which are closed when relay I2 is released, to junction point 3|, where it divides into two branches. One branch passes through resistance 32 to junction point 33 where it connects to the top plate of condenser I9 and the lefthand element or starting anode of the threeelement cold cathode type gas discharge tube or triggertubeasitisgenerallyknown. The second branch passes through the left-hand winding of relay I2 to the middle element or anode of tube l8. Negative battery is connected through conductors 23 and 34 to the bottom plate of condenser l9 and the right-hand element or cold cathode of tube l8.

Resistance 32 is intended to limit the flow of charging current to condenser l9. When the condenser I! has been sufficiently charged, its voltage and the voltage of the control anode will be raised sufficiently to permit the tube l8 to fire and a flow of current will be established between the anode and cold cathode of tube l8 energizing the left-hand winding of relay l2, reoperating relay l2. The reoperation of relay I! will reestablish the energizing circuit of magnet IS. The constants of the resistance 32 and condenser |9 are fixed so that the desired interval will elapse before tube I8 fires and magnet l3 Ls, reenergized. When relay I2 is reenergized, positive battery is disconnected from the top plate of the condenser, the control anode of tube I8, the left-hand winding of relay l2 and the anode of tube l8 when contact 30 is opened The closing of contact 35 when relay I2 is reoperated completely discharges condenser IS. The operation of relay l2 also closes contact 22 and reestablishes the path through the right-hand winding of relay 22, heretofore traced, to hold relay 22 normally operated.

Attention is called to the fact that under the system of operation described for tube l8 and relay 12, current passes through tube l8 far a very short interval only, namely, long enough to permit relay l2 to operate, Voltage is applied to the tube only during the delay interval. A shunt is maintained around the condenser at all times except during the delay intervaL. The condenser is therefore completely discharged at the beginning of the interval. The periods measured should therefore be of uniform duration and the period of usefulness of the tube should be a maximum.

In the arrangement shown on the drawing and described in detail above, only one function lever contact, namely contact II, is shown. The resistance 32 and the condenser l9 are each shown as units. In actual operation, it is to be understood that as difi'erent functions require different intervals, there will be different delay intervals required. If the longest delay required for the longest function is provided in the circuit, line time will be wasted.

It is possible, of course, to reproduce the delay circuit disclosed herein in its entirety for each delay interval required but, as a practical matter, in cases where it is desirable to provide different delay intervals for different functions, a-

number of function lever controlled contacts such as II will be provided and any of a number of arrangements of the resistance and condenser will be used which will readily suggest themselves to those skilled in the art, wherein the amount of resistance 32 and capacitance I9 is varied by means of a switching operation to provide the desired delay without providing a separate tube such as l8 in each case.

What is claimed is:

1. In a teletypewriter switching system, a transmitter connected through an operable telegraph path to a receiver, electromechanical means for starting and stopping said transmitter responsive to a control circuit and electric circuit delay means in said control circuit responsive to the transmission of certain signals from said transmitter for stopping said transmitter for a measured interval.

2. In a teletypewriter transmitting and receiving system, a teletypewriter transmitting device connected to a teletypewriter receiving device and means, connected to said transmitter, responsive to the transmission of specific signals from said transmitter for stopping the transmission of signals from said transmitter for a measured interval after said receiver has completed performing its function in response to said signals.

3. In a teletypewriter transmitting system, a teletypewriter signal transmitter, means connected to said transmitter for starting said transmitter and automatic means connected to said transmitter for stopping said transmitter, in response to the transmission of specific signals from said transmitter, for a definite measured interval longer than that required to record said signals.

4. In a teletypewriter transmitting system, a tape perforator for perforating code signals in a tape, means for delivering tapefrom said perforator directly to transmitting means for transmitting signals in accordance with said perforations and transmitting control means connected to said transmitter responsive to the perforation of a particular code in said tape for stopping said transmitter for a measured interval after said code has been recorded.

5. A system in accordance with claim 4 including means for automatically restarting aid transmitting means after said measuredinterval.

6. A system in accordance with claim 4 in which said control means comprises an electric potential controlled discharge device.

7. A system in accordance with claim 4 in which said control'means comprises a function lever in a teletypewriter receive. and an electrical delay circuit responsive to said lever.

8. In a teletypewriter transmitting system, a tape perforator for perforating code signals in a tape, means for delivering said tape from said perforator directly to transmitting means for transmitting signals in accordance with said perforations, transmitting control means connected to said transmitter responsive to the perforations of a particular code in said tape for stopping said transmitter for a measured interval, said control means comprising a delay circuit.

9. In a teletypewriter transmitting system, a tape perforator for perforating code signals in a tape, means for delivering said tape from said perforator directly to transmitting means for transmitting signals in accordance with said perforations, transmitting control means connected to said transmitter responsive to the perforations of a particular code in said tape for stopping said transmitter for a measured interval, said control means comprising a teletypewriter receiver and a delay circuit responsive to said teletypewriter receiver.

10. In a teletypewriter transmitting and receiving system, a transmitting device connected to a plurality of receiving devices, means in said transmitting device for conditioning said transmitting device to transmit signals of a particular character to said receivers requiring relatively long intervals for recording by said receivers, individual recording apparatus connected to each of said receiver's requiring intervals of different lengths for the performance of said recording on the different receiving devices and a synchronizing device connected to said transmitting device to compensate for the variations in the required recording time.

11. A system in accordance with claim 10 in which the synchronizing device comprises a teletypewriter receiver.

12. A system in accordance with claim 10 in which the synchronizing device comprises a delay circuit.

13. A system in accordance with claim 10 in which the synchronizing device comprises a teletypewriter receiver and a delay circuit.

14. A system in accordance with claim 10 in which the synchronizing device comprises a means for stopping the transmitter momentarily.

15. In a teletypewriter a single transmitter operably connected to a plurality of receivers, means for transmitting signals of a first general character from said transmitter, means in said receivers for printing typed characters in response to said signals, means for transmitting signals of a second general character from said transmitter, means for adjusting the printed record in each machine in response to signals of said second character, individual mechanisms associated with each receiver responsive to signals of said second character, said mechanisms requiring intervals of different lengths for said adjustment, and means in said transmitter operating in response to the transmission of signals of said second character only to compensate for said required intervals of difierent length.

16. A system in accordance with claim 15 in which saidcompensating means comprises a telet-ypewriter receiver.

1'7. A system in accordance with claim 15 in which said compensating means comprises a delay circuit.

18. A system in accordance with claim 15 in which said compensating means comprises a, teletypewriter receiver controlling a delay circuit 19. A system in accordance with claim 15 in,

which said compensating means comprises a teletypewriter receiver controlling a delay circuit,. which delay circuit in turn controls said transmitter.

WILMARTH Y. LANG. 

